Mandatory eight-year jail sentences for fatal one-punch attacks fuelled by alcohol or drugs are among are raft of measures to be introduced to curb alcohol-related violence in Sydney.

The so-called one-punch laws, announced by New South Wales Premier Barry O'Farrell today, include expanded Sydney CBD lockout zones, a freeze on new liquor licences, and the statewide closure of bottle shops at 10:00pm.

Sentences for serious assaults involving alcohol will also be increased by two years.

"It is no longer acceptable to go out and drink yourself stupid, take illicit substances, start fights, 'coward punch' people or engage in other assaults thinking you [will] get away with it," Mr O'Farrell said.

"Mandatory is the key word here. The judge has no choice now. It's welcome news," Kelly's father Ralph said.

"It's bittersweet to know that the reform will come in shortly, but it's also still terrible for us as a family," Mr Kelly said.

"It's sad we had to bring in this change and that our community has to have these laws but if that's the only way we can... make cultural change and social change and stop thugs from hitting people, then so be it."

Expanded lockout zone stretches from Kings Cross to Darling Harbour

Under the laws, there will be a mandatory 1:30am lockout for licensed premises across an expanded Sydney CBD entertainment precinct, spanning from Kings Cross to Darling Harbour.

Drinks will not be allowed to be served after 3:00am, but premises can remain open.

Small bars, casinos, restaurants and tourist accomodation facilities will be exempt from the laws.

"As I understand it, there are less than a dozen small bars across the CBD area and most are closed by 2:00am anyway."

Periodic risk-based licensing will also be introduced for some venues.

The Government has been pressured to crack down on alcohol-fuelled violence since Kelly's death, with the debate reignited by the fatal one-punch assault of teenager Daniel Christie in Kings Cross on New Year's Eve.